take your ruber flaten it (if its not already) and cut it (if its not) in a oval.cut a small hole in the top or two on the side if you want to make it into a necklace
now take the other rubber material (eraser like) and cut that into the exact same size as your oval.
draw on the eraser material a tree i used a pic from the internet when you have traced it carve out everything except your drawing u formed your stamp
use your blue paint dosent really matter what color and paint the stamp u made if you want it to last use water proof paint
print it down on your rubber oval
when it drys cover the painted side with clear glue and water
let it dry and attach the string through the holes u have your necklace good luck!!!